This application is a competing supplement to the Genetics of Microangiopathic Brain Injury (GMBI) study (R01-NS41558), an ancillary study to the Family Blood Pressure Program (FBPP) and Genetic Epidemiology Network of Arteriopathy (GENOA) study (U01-HL54464, U01-HL54463, and U01-HL54457). These projects share an overall objective to identify genetic determinants of hypertension and its cerebral, cardiac, and renal complications in multiple ethnic groups. In particular, the GMBI study, which has spawned this competing supplement, is identifying and characterizing genetic variation contributing to inter-individual differences in ischemic damage to the subcortical white matter of the brain, referred to as leukoaraiosis [unreadable] [unreadable] This proposed supplement will investigate whether comprehensive measures of blood pressure (BP), determined by 24-hour ambulatory monitoring (ambulatory BP), and quantitative measures of ischemic damage to the subcortical white matter of the brain (i.e., leukoaraiosis), determined by magnetic resonance imaging (MRI), can enhance understanding of the impact of BP on cognition. Since the volume of leukoaraiosis and comprehensive measures of neurocognitive function are already being collected in GMBI subjects, we propose adding ambulatory BP measurements in sub-samples of 250 non-Hispanic black and 250 non-Hispanic white GMBI participants. [unreadable] [unreadable] Aim 1 will determine whether ambulatory BP measures including daytime, nighttime, and whole day BP level, pulse pressure, and diurnal variation predict inter-individual differences in measures of neurocognitive function in 250 African American and 250 non-Hispanic white GMBI participants. Aim 2 will determine whether the MRI volume of leukoaraiosis modifies or explains the relationships between measures of ambulatory BP and measures of cognitive function evaluated in aim 1. [unreadable] [unreadable]